Heat recovery boiler with bypass



Nov. 11, 1969 F.GETH1NG HEAT RECOVERY BOILER WITH BYPASS 2 Sheets-Sheet1 Filed Dec. 22, 1967 N w )NN ANN NNVJ MN RNs www Nw www (lvl www/WM w I(VWM (Will um Nov. 11, 1969 F. GETHING HEAT RECOVERY BOILER WITH BYPASS2 Sheets-Sheet 2 Filed Dec. 22. 1967 United States Patent O 3,477,411HEAT RECOVERY BOILER WITH BYPASS Frank Gething, Milwaukee, Wis.,assignor to Aqua-Chem, Inc., a corporation of Wisconsin Filed Dec. 22,1967, Ser. No. 692,836

Int. Cl. F22b 9/12 U.S. Cl. 122-7 25 Claims ABSTRACT OF THE DISCLOSURE Aboiler connected to an external source of heated medium, such as theexhaust of a turbine or engine; and including means for bypassing theheated medium around the heat exchange tubes. The bypassing means is inthe form of an insulated furnace drum extending through the heatexchange chamber; and the furnace drum and the heat exchange tubescontain means for silencing the sound of the source of heated medium. Aconverging nozzle is provided at the entrance end of the furnace drumfor drawing cooling air in through the heat exchange tubes during abypassing operation to compensate for any heat given to the heatexchange chamber through the furnace drum.

Background of the invention This invention relates in general to heatexchange apparatus, and more particularly to a boiler wherein water in aheat exchange chamber is converted into steam by having a heated mediumflow through a plurality of heat exchange tubes in the heat exchangechamber.

One of the most common types of boilers is the socalled fretube boiler,and such structures have usually included a furnace tube or drum in theheat exchange chamber, with a burner or the like being provided at oneend of the iretube, and with baffle means being provided for directingthe products of combustion in one or more passes through the heatexchange tubes. Many suggestions have been made in the past forirnproving the efficiency of such boilers, and one such solution hasbeen to utilize the products of combustion from an external source, suchas from a turbine or engine, as the heat exchange medium. Thissuggestion obviates the necessity of providing a self-contained burnerunit within the boiler, and also makes use of the heat carried in theexhaust gases, which would normally flow to atmosphere.

One of the chief drawbacks of the above suggestion is that the demandsfor steam from a boiler are usually sporadic, and do not necessarilycoincide with the period during which the external source of heatexchange medium is used. In many installations, prime movers such asengines and turbines are operated continuously, and if the products ofcombustion were continuously circulated to a boiler, there would be anobvious wastage of steam, during periods when there was no demand forsteam. One solution to this problem is to physically disconnect theexternal source of heat exchange medium from the boiler during periodswhen steam is not needed, but this is obviously a time consuming andundesirable step. Applicant has solved this problem in a unique mannerby providing means within the boiler itself by which the heated mediumcan bypass the heat exchange tubes. While this solution has obviated thenecessity of disconnecting the source of heat exchange medium from theboiler, it has created a further problem, in that the heat exchangemedium flowing in the bypass path through the boiler also gives up heatto the water within the boiler, which may produce steam when it is notneeded.

Summary The present invention provides a unique arrangement whereby anyheat imparted to the water during the bypassing of heat exchange mediumthrough the boiler may be compensated by drawing cooling ambient airthrough the heat exchange tubes during the bypassing operation. Toachieve this, the plenum chamber at the exhaust end of the boiler isdivided into two compartments, one communicating with the exhaust end ofthe heat exchange tubes, and the other communicating with the exhaustend of a furnace drum that is used to bypass the heat exchange mediumthrough the boiler. The entrance end of the furnace drum is incommunication with the plenum chamber at the opposite end of the boiler,which also communicates with the entrance end to the heat exchangetubes. A converging nozzle is provided in the entrance of the furnacedrum, and during a bypassing operation, the heat exchange medium that isaccelerated by the converging nozzle draws cooling air through the heatexchange tubes, with the cooling air passing through the furnace drumwith the heat exchange medium. The furnace drum includes a damper, whichmay be closed during normal heating operation of the boiler, so that theheated medium will flow through the heat exchange tubes. During abypassing operation, the damper may be opened to a selected positionwherein the cooling effect of the ambient air drawn through the heatexchange tubes will balance the heating elfect due to the heat exchangemedium owing through the furnace drum. To minimize the heating effect ofthe heat exchange medium during a bypassing operation, an insulatingliner or sleeve is provided within the furnace drum, and convenientlythe sleeve may include silencing means for muiiiing any noises emanatingfrom the source of heat exchange medium.

Brief description of the drawings FIG. 1 is a vertical section through.a boiler that is formed in accordance with the principles of the presentinvention;

FIG. 2 is a view taken generally along line 2-2 of FIG. 1;

FIG. 3 is a view taken generally along line 3-3 of FIG. 1; and

FIG. 4 is a view taken generally along line 4-4 of FIG. 1.

Desecript-ion of the preferred embodiment While this invention issusceptible of embodiment in many different forms, there is shown in thedrawings and will herein be described in detail an embodiment of theinvention with the understanding that the present disclosure is to beconsidered as an exemplication of the principles of the invention and isnot intended to limit the invention to the embodiment illustrated. Thescope of the invention will be pointed out in the appended claims.

Referring now to the drawings in detail, the boiler of the presentinvention is indicated in its entirety at 10 in FIG. l, and the boiler10 is supported on legs 12 that extend upwardly from base 11. Boiler 10includes substantially cylindrically shaped shell 13 having outwardlyextending flanges 14 and 15 at opposite ends thereof, and end caps 16and 17 have outwardly extending flanges 18 and 19, respectively, securedto shell flanges 14 and 15 by suitable means, such as by bolts or bywelding. End caps 16 and 17 each include suitable refractory orinsulating material 20 and 21, respectively, and plenum chambers 22 and23 are provided inwardly of the end caps 16 and 17 at opposite ends ofthe boiler.

A `pair of spaced tube sheets 24 and 25? extend generally transverselywith respect to the axis of shell 13, and tube sheets 24 and 25 aresecured to the shell 13 in water tight fashion to provide a heatexchange chamber 26 therebetween. A plurality of openings 27 areprovided in tube sheet 24, and a plurality of openings 28 are providedin tube sheet 25, with each opening 27 being aligned with an opening 28.A plurality of heat exchange tubes 29 are provided in chamber 26, withone end of each tube 29 being secured in water tight fashion around anopening 27 and the other end of tube 29 being secured in water tightfashion around opening 28. Boiler includes a conventional steam nipple30 for withdrawing steam from chamber 26, and the boiler may alsoinclude pressure relief valves such as those shown at 31.

Tube sheets 24 and 25 include enlarged openings 32 and 33 adjacent thelower end thereof that are aligned with one another. A cylindricalfurnace tube or drum 34 extends through the lower portion of chamber 26,and the right hand end (as viewed in FIG. l) of drum 34 is secured inwater tight fashion to tube sheet 25 outwardly of opening 33, while theopposite end of drum 34 is secured in water tight fashion within opening32 in the tube sheet 24. As is clear from FIG. l, drum 34 includes anend portion 34a that extends outwardly of tube sheet 24 into plenumchamber 22, and the purpose of this will be hereafter explained.

A generally U-shaped baille 35 extends outwardly from tube sheet 24 intoplenum chamber 22, and baille 35 surrounds the end 34a of furnace drum34, as can be best seen in FIG. 3. A generally vertically extendingbaille 36 extends upwardly from baille 35 in plenum chamber 22, dividesthe plenum chamber into two compartments 37 and 38. An annular ring ofrefractory or insulating material 39 extends around plenum chamber 22,and an opening 40 in the upper end of refractory material 39 establishescommunication between plenum chamber 22 and an exhaust stack 41, whichcommunicates with atmosphere. An outwardly extending flange 42 on stack41 is joined to an outwardly extending flange 43 on a chimney 44 bysuitable fastening means, such as bolts or the like, and a partition 45extends through stack 41 and chimney 44, with the lower end of partition45 being secured to the upper end of partition 36. Partition 45 dividesstack 41 and chimney 44 into compartments 46 and 47 which communicate,respectively, with compartments 37 and 38 of plenum chamber 22. Afurther baille 48 may extend inwardly from end cap 16 into compartment38 of plenum chamber 22, for diverting gases emanating from the furnacedrum 34 through a tortuous ow path.

Boiler 10 includes means for connecting the boiler to an external sourceof heated medium, such as the exhaust from a turbine or engine, and saidmeans may include a tubular member 50 that is connected to the exhaustof the external heated medium source, with an outwardly extending flange51 on member 50 being secured to the outer face of end cap 17. The flowof heated medium from the external source in represented by the arrow 52in FIG. 1, and the boiler 10 includes means for accelerating the flow ofheated medium into the furnace durm 34, with the accelerating meansbeing illustrated in the form of a converging nozzle 53 in FIG. 1.Nozzle 53 may have an outwardly extending flange 54 secured to the outersurface of end cap 17, and illustratively, the flange 54 on nozzle 53may be positioned under the flange 51 on member 50, with commonfasteners securing both flanges to the end cap 17. As is evident fromFIG. 1, the nozzle 53 extends entirely through plenum chamber 23, andthe end portion 53a of nozzle 53 extends slightly inwardly of furnacetube 34 through the opening 33 in tube sheet 25.

As can be best seen in FIG. 1, a generally cylindrically shaped liner orsleeve 55 is positioned in furnace drum 34, and sleeve 55 extendsoutwardly through opening 33 in tube sheet 25, with an outwardlyextending flange 56 of sleeve 55 being secured to the tube sheet 25around opening 33 by suitable fasteners. As is evident from FIG. l,sleeve 55 is effectively a cantilevered member, in that it is supportedentirely by having its flange 56 secured to the tube sheet 25. Thiscreates an annular air gap 57 between sleeve 55 and furnace drum 34,which serves to insulate the furnace drum from the heated medium flowingthrough sleeve 55, as will hereinafter appear. While sleeve 55 isillustrated in FIG. 1 as a cylindrical member unsupported throughout itslength, the present invention contemplates that other forms ofinsulating liners may be used, and one such means would be a corrugatedtubular member with the outer surface of the corrugation either beingspaced from the furnace drum wall, or resting thereagainst to create aseries of spaced air pockets. Furthermore, the present invention alsocontemplates that one or more simple supports may be provided for thesleeve 55 to enable the sleeve 55 to move slightly relative to thefurnace drum 34 in response to the differences in temperaturetherebetween.

Means is provided for silencing or mullling any noises emanating fromthe external source of heated medium during a bypassing operation, andsaid means includes a plurality of sound deadening llow impedimentspositioned at longitudinally spaced positions within sleeve 55. As canbe seen in FIG. 1, the flow impediments include a plurality of spaceddiscs 58 having a diameter less than the diameter of sleeve 55, with thediscs 5S being disposed generally transversely with respect to the flowof heated medium through the sleeve 55, and being secured thereto by aplurality of rods, not shown. A disc 59 is interposed between discs 58,and disc 59 includes a central opening 59a substantially the samediameter as discs 58, so that the heated medium must flow through atortuous path past the impediments 58 and 59. A further llow impedimentis carried upon a disc 6l) that is disposed generally transversely withrespect to the flow of heated medium through the sleeve 55, and thislatter impediment takes the form of a plurality of tubes 61, three inthe illustrated embodiment, with the tubes 61 being secured to disc 69.The axes of tubes 61 are disposed generally parallel with respect to theaxis of sleeve 55, and the entrance end of tubes 61 is positioned inalignment with the adjacent disc 58, so that the heated medium must tlowthrough a tortuous path in entering the tubes 61. A further disc 58 ispositioned in alignment with the outlet end of tubes 61, as is clearfrom FIG. 1, so that the heated medium must llow around the outerperiphery of disc 58 in passing outwardly of the end of sleeve 55, whichis disposed somewhat inwardly of tube sheet 24.

An adjustable flow control device is provided in furnace drum 34, and inthe illustrated embodiment, the flow control device is in the form of abutterfly damper 62 that is carried on a pivotally mounted control rod63. Since furnace drum 34 has an extension 34a that extends outwardly oftube sheet 24, control rod 63 is positioned in the dry portion of theboiler outwardly of chamber 26. Damper 62 is movable from a maximumheating position shown in full lines in FIG. l wherein the flow ofheated medium through furnace drum 34 is blocked, and a maximum heatcompensating position shown in broken lines in FIG. 1, wherein thedamper offers substantially no retardation to the flow of heated mediumthrough the furnace drum 34.

During a heating operation, and assuming damper 62 to be in the fullline position of FIG. 1 completely blocking tlow of heated mediumthrough furnace drum 34, it will be apparent that the heated medium willflow through the annular passage 64 between the end 53a of nozzle 53 andsleeve 55 into plenum chamber 23. The ilow of heated medium in a heatingoperation is represented by the full line arrows 65, and it will benoted that the heated medium flows from plenum chamber 23 through tubes29 in heat exchange relationship with the fluid in chamber 26 intocompartment 37 of plenum chamber 22, and thence into compartment 46 ofstack 41 and chimney 44. While only a single pass boiler has beenillustrated and described herein, that is, a boiler wherein the heatedmedium flows directly from one end of the boiler through the heatexchange tubes to the other end of the boiler and thence to atmosphere;it will be apparent to those skilled in the art that suitable bafflingmeans may be provided in plenum chamber 23 and in compartment 37 ofplenum chamber 22 for directing the heated medium in plural passesthrough the heat exchange tubes 29. Each of the heat exchange tubes 29includes means for mullling or silencing any noises emanating from thesource of heated medium, and in the illustrated embodiment, thesilencing means takes the form of a plurality of dimples 29a provided atspaced positions along each of the tubes 29. Dimples 29a may take theform of those described in Cleaver et al. Patent 3,230,936 and Loebel etal. Patent 3,232,280;

The dimpled tubes 29 provide a llow path for the heated medium having apressure drop which is greater than the pressure drop presented by allow path through sleeve '55. Thus, when it is desired to bypass theheated medium around heat exchange tubes 29, the damper 62 is adjustedto a position unblocking furnace drum 34 to an extent where the pressuredrop through furnace drum 34 is less than the pressure drop through heatexchange tubes 29. This damper position will be intermediate the fulland broken line positions illustrated in FIG. l, and with the damper inthis position, the heated medium llowing into sleeve 55 from nozzle r53will follow the path represented by the broken line arrows 66 around thesilencing impediments 58-61 outwardly of sleeve 55, around damper `62,outwardly of furnace drum 34, around baille 35, into compartment 38 ofplenum chamber 22, around baille 48, into compartment 47 of stack 41 andchimney 44 and to atmosphere.

When the damper 62 is in the maximum heat compensating position shown inbroken lines in FIG. 1, the heated medium accelerated by nozzle 53 willapply a suction to annular area 64 and plenum chamber 23, thus drawingcooling ambient air into the boiler. The path of the cooling air isrepresented by the broken line arrows 67, and it will be noted that thecooling air flows downwardly in compartment 46 of stack 41 and chimney44 into compartment 47 of plenum chamber 22, through heat exchange tubes29 thereby cooling the lluid within chamber 26, and into the plenumchamber 23, Where the cooling air then flows through annular opening 64into the liner 55 where it passes with the heated medium in its llowpath to atmosphere. It will be appreciated that the insulating air gap57 between sleeve 55 and furnace drum 34 effectively prevents a greatdeal of heat from passing to the fluid within chamber 26 through thewalls of drum 34, and that the damper 62 may be adjusted to a positionwherein the flow of ambient air through the tubes 29 off-sets any heatthat is imparted to the fluid within chamber 26 through the wall offurnace drum 34. It will further be apparent that during a heatingoperation, the damper 62 may be adjusted to a position wherein a portionof the heated medium flows through the heat exchange tubes 29 and afurther portion of the heated medium flows through the furnace drum 34to thereby modulate the heating effect.

I claim:

1. A boiler comprising: means defining a casing having a chambertherewith adapted to contain a fluid; a tube sheet closing each end ofthe chamber; a plurality of spaced tubes in said chamber and openingoutwardly of said tube sheets, said tubes being adapted to be in heatexchange relationship with the lluid in said chamber; an exhaust stack;and alternatively selective means, for either directing a heated mediumin a first path through said tubes in heat exchange relationship withsaid fluid, or for directing said heated medium in a second path towardthe exhaust stack to bypass said tubes.

2. A boiler as set forth in claim 1 wherein said means for directing aheated medium through said tubes includes means for establishingcommunication between a source of said heated medium and one end of atleast some of said tubes, and means for establishing; communicationbetween atmosphere and the other end of at least some of said tubes.

3. A boiler as set forth in claim 2 wherein said means for directingheated medium toward the exhaust stack to bypass said tubes includesmeans for establishing communication between said source of heatedmedium and said exhaust stack, said last named means including analternatively selective device that is movable to a maximum heatingposition blocking communication between said source of heated medium andsaid exhaust stack, whereby said heated medium will tlow through saidtubes and thence to atmosphere.

4. A boiler as set forth in claim 3 wherein said device is movable to aheat compensating position establishing communication between saidsource of heated medium and said exhaust stack, said means forestablishing communication between said source of heated medium and saidone end of at least some of said tubes cooperating with at least aportion of said means for establishing communication between said sourceof heated medium and said exhaust stack when said device is in said heatcompensating position to apply a suction to said one tube ends, wherebycooling air is drawn inwardly through said tubes and flows with saidheated medium through said means establishing communication between saidsource of heated medium and said exhaust stack.

5. A boiler as set forth in claim 4 wherein the pressure drop of heatedmedium flowing through the means establishing communication between thesource of heated medium and the exhaust stack is less than the pressuredrop of heated medium flowing through the means establishingcommunication between the source of heated medium, tubes and atmosphere.

6. A boiler as set forth in claim 4 in which said source of heatedmedium is external of said boiler, and wherein means is provided in bothsaid first and second paths for deadening sound from said source ofheated medium.

7. A boiler as set forth in claim 6 wherein the sound deadening means insaid first path includes a series of dimples in each of said tubes.

8. A boiler as set forth in claim 6 wherein said means for establishingcommunication between said source of heated medium and said exhauststack includes a furnace drum extending through said chamber andcommunieating at one end with said source of heated medium andcommunicating at the other end with said exhaust stack, sound deadeningmeans in said second path being provided in said furnace drum.

9. A boiler as set forth in claim 8 wherein a portion of said furnacedrum extends outwardly beyond the tube sheet closing the end of thecasing remote from said source of heated medium.

10. A boiler as set forth in claim 9 wherein said alternativelyselective device is positioned in the outwardly extending portion ofsaid furnace drum.

11. A boiler as set forth in claim 8 wherein a generally tubular sleeveis positioned in said furnace drum, at least a portion of said sleevebeing spaced from said furnace drum to define an insulating spacetherebetween.

12. A boiler as set forth in claim 11 wherein said sleeve extends intosaid furnace drum from the end of the furnace drum adjacent the sourceof heated medium, said sleeve being spaced from said furnace drumthroughout its length.

13. A boiler as set forth in claim 11 wherein the sound deadening meansin said second path includes a series of impediments to the flow ofheated medium at longitudinally spaced locations in said sleeve.

14. A boiler as set forth in claim 12 wherein said means forestablishing communication between said source of 7 heated medium andsaid exhaust stack further includes a nozzle communicating with saidsource of heated medium and having a convergent portion extending intosaid sleeve.

15. A boiler as set forth in claim 14 wherein said nozzle portion isspaced from said sleeve to define an annular area therearound.

16. A boiler comprising: a generally cylindrical shell; a pair of spacedtube sheets adjacent opposite ends of said shell and defining a chambertherebetween that is adapted to contain a fluid; means defining a firstplenum chamber outwardly of one tube sheet; means defining a secondplenum chamber outwardly of the other tube sheet; partition meansdividing said second plenum chamber into first and second compartments,each of said compartments communicating with atmosphere; a plurality ofspaced tubes extending between said tube sheets in said chamber, saidtubes communicating at one end with said first plenum chambers and atthe other end with the first compartment of said second plenum chamber;a furnace drum in said chamber and communicating at one end with saidfirst plenum chamber and with a source of heated edium, the other end ofsaid furnace drum communicating with the second compartment of saidsecond plenum chamber; and an adjustable control member selectivelymovable between (a) a maximum heating position blocking said furnacedrum so that said heated medium flows into said first plenum chamber,through said tubes to the rst compartment of said second plenum chamber,and thence to atmosphere, (b) a maximum heat compensating positionunblocking said furnace drum so that said heated medium bypasses saidtubes and cooling air is drawn into the first compartment of said secondpienum chamber, said cooling air owing through said tubes into saidfirst plenum chamber, and thence flowing with said heated medium throughsaid furnace drum into the second compartment of said second plenumchamber and thence to atmosphere, (c) and a series of heat modulatingpositions intermediate of said maximum heating position and said maximumheat compensating position.

17. A boiler as defined in claim 16 wherein a converging nozzlecommunicates with said source of heated medium and extends through thefirst plenum chamber with the end of the nozzle being positionedinwardly of the end of said furnace drum, the end of said nozzle beingspaced from said furnace drum to define an annular space therebetweenestablishing communication between said furnace drum and said firstplenum chamber.

18. A boiler as dend in Claim 16 wherein a single exhaust stackcommunicates with said second plenum charnber, said exhaust stackincluding partition means therein dividing the interior of the exhauststack into a first compartment that communicates with the firstcompartment of said second plenum chamber and a second compartment thatcommunicates with the second compartment of said second plenum chamber.

19. A boiler connected to an external source of heated medium, such asthe exhaust of a turbine or engine, comprising: means defining a casinghaving a chamber therewithin adapted to contain a fluid; a pair of tubesheets closing each end of the chamber; a plurality of spaced tubes insaid chamber, said tubes being adapted to be in heat exchangerelationship with the fluid in said chamber; an exhaust stackcommunicating with one end of said tubes; means establishingcommunication between said source of heated medium and the other end ofsaid tubes; and means for silencing sound emanating from said source ofheated medium.

20. A boiler as set forth in claim 19 wherein said sound silencing meansis associated with said tubes.

21. A boiler as set forth in claim 18 including means for bypassingheated medium away from said tubes, said sound silencing means beingassociated with said bypassing means.

22. A boiler connected to an external source of heated medium, such asthe exhaust of a turbine or engine, comprising: means defining a casinghaving a chamber therewithin adapted to contain a uid; a pair of tubesheets closing each end of the chamber; a plurality of spaced tubes insaid chamber, said tubes being adapted to be in heat exchangerelationship with the fluid in said chamber; an exhaust stackcommunicating with one end of said tubes; means establishingcommunication between said source of heated medium and the other end ofsaid tubes; and means for bypassing heated medium around said tubes tosaid exhaust stack.

23. A boiler as set forth in claim 22 wherein said bypassing meansincludes a drum in said chamber and extending from end to end thereof,said drum communicating at one end with said source of heated medium andat the other end with said exhaust stack.

24. A boiler as set forth in claim 23 including means in said drum forinsulating the drum from the flow of heated medium.

25. A boiler as set forth in claim 24 wherein a sleeve is provided insaid drum, with at least a portion of said sleeve being spaced from saiddrum to define said insulating means.

References Cited UNITED STATES PATENTS 1,734,310 11/1929 Taylor 122-1491,994,026 3/1935 Pierce 122-23 2,080,404 5/1937 Hunter et al 122-1492,576,053 11/1951 Toner 122-149 XR 3,231,016 1/1966 Stewart et al. 122-7XR 3,269,360 8/1966 Adams 122-7 FOREIGN PATENTS 774,799 5/ 1957 GreatBritain.

KENNETH W. SPRAGUE, Primary Examiner U.S. Cl. X.R. 122-135, 149

